It is more and more important to consume energy efficiently and protect the environment. Accordingly, hybrid vehicles are becoming main stream trends, which are efficient, energy-saving and environment protecting. Hybrid vehicles relate to techniques on vehicles, power sources, electronics, computers and controls, which have been researched and developed for more than 10 years in the world. Industrialization of the hybrid vehicles has been achieved by Toyota Corp. and Honda Corp., Japan. Hybrid vehicles have also been researched and developed widely in China.
Power systems for hybrid vehicles can be divided into three basic types, i.e. series arrangement, parallel arrangement, and the hybrid arrangement, as well as various variants, each having its own advantages and disadvantages. Typical examples are the THS hybrid system of the Prius Hybrid car of Toyota Corp., and the IMA parallel system of the Insight Hybrid car of Honda Corp. The THS system is a hybrid arrangement type, which connects an internal combustion engine with a generator and a motor via planetary gears. A part of the power source from the internal combustion engine is transmitted to a final drive via a planetary carrier and a ring gear of planetary gears, while another part drives the generator via the planetary carrier and a sun gear of the planetary gears, and then the electric power generated from the generator drives the motor. The two parts of the powers are transmitted to the driving wheels to drive the vehicle via the final drive and the drive shaft. The rest of the power from the internal combustion engine is used to charge the power battery via the generator. An electric motor can drive the vehicle independently in a pure electric-driving mode, which can recover most of the braking energy. The IMA system is a parallel arrangement type, in which a motor (motor and generator combined together) is arranged between an internal combustion engine and a clutch. The motor can start the internal combustion engine and also supply supplementary power. Since it is connected with the internal combustion engine directly, the motor can't drive the vehicle independently, accordingly no pure motor driving mode exists, and much less of the braking energy can be recovered.
The Prius THS system of Toyota Corp has multiple driven modes, strong hybrid propulsion but with complicated structure, great power of motor, and high manufacturing cost. Since a part of the power from the internal combustion engine is transformed twice from mechanical power to electric power and then electric power to mechanical power again, the transmitting efficiency of the entire system is low. The IMA system of the Insight Hybrid car of Honda Corp. has simpler structure, lower manufacturing cost, however it has less driving modes, weaker hybrid propulsion, more energy-consumption and more exhaust gas emission than those in the Prius THS system of Toyota Corp.